1. Field of the Invention
This invention is concerned with improving the flow properties and pour point characteristics of residual fuels. More particularly, this invention is concerned with fuel compositions comprising a residual fuel and an effective pour depressant amount of an oil-soluble terpolymer.
2. Description of the Prior Art
As is well known, residual fuel oils contain quantities of wax and asphaltic compounds which render them viscous and interfere with practical use of such oils. In particular, serious problems are encountered in pumping residual fuel oils to a burner and in making them flow at low temperatures. Other factors to be reckoned with are that these oils behave as non-Newtonian liquids at low temperatures; exhibit variable solidifying temperatures and peculiar hysteresis phenomena, all of which make for difficulties in equipment design.
One approach in making these oils easier to handle has been to subject them to fairly lengthy dewaxing procedures.
Another approach which has been used to bring the viscosity of residual fuel oils to suitable levels has been to dilute or "cut" them with a major amount of lighter distillate oils but this is an expensive procedure because of the considerably higher cost of the distillate oils relative to the residual oils.
A number of additives have been suggested and tried with success in lubricating oils and in so-called middle distillates in order to tie in the wax therein and improve flow at low temperatures. Such additives consist either of compounds formed by alkylating benzene or naphthalene derivatives or of copolymers of ethylene-vinyl fatty acid ester of a molecular weight up to 3000 and containing from 15 to 25% by weight of the vinyl saturated aliphatic monocarboxylic acid ester. These additives are not, however, effective in depressing the pour point of residual fuel oils.
It is therefore the main object of the present invention to improve the pour point characteristics of residual oils without using elaborate dewaxing procedures.
An equally important object of this invention is to provide heating oils and fuel oils having improved pour point characteristics by incorporating therein a minor amount of certain terpolymer pour depressants.